A student investigates the reaction between magnesium and hydrochloric acid to determine the order of reaction with respect to hydrochloric acid. The student is supplied with 2.00 mol dm⁻³ hydrochloric acid and six identical, clean pieces of magnesium ribbon. In experiment 1, the student places 50 cm³ of 2.00 mol dm⁻³ hydrochloric acid in a 100 cm³ beaker and adds a piece of magnesium ribbon to the acid in the beaker. The student records how long it takes for the magnesium ribbon to disappear. The student carries out five further experiments, diluting the 2.00 mol dm⁻³ hydrochloric acid each time to provide results from five different concentrations of acid. The student carries out each experiment in a 100 cm³ beaker.

1. (a)(i)Complete the table so the student can use it to record the reaction time for each experiment. The table should include suggested volumes of acid and water for each experiment. Columns should be suitably labelled. [2][2]
2. (a)(ii)Identify the dependent variable in this experiment. [1][1]
3. (a)(iii)Apart from the magnesium ribbon, identify one variable that should be controlled in these experiments. [1][1]
4. (b)Explain why the student's proposed method of determining the reaction time may lead to inaccuracies in the recorded results. [1][1]
5. (c)Suggest one other variable that could be measured to determine the order of the reaction. [1][1]